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kludex/starlette

12,308PythonAudience · developerComplexity · 3/5LicenseSetup · easy

TLDR

Starlette is a lightweight Python library for building fast web APIs and services, it handles routing, WebSockets, middleware, and background tasks, and serves as the foundation that FastAPI is built on.

Mindmap

mindmap
  root((starlette))
    Core Features
      Routing
      WebSockets
      Middleware
      Background tasks
    Optional Features
      Templates
      Form parsing
      Sessions
    Tech Stack
      Python
      ASGI
      Uvicorn
    Use Cases
      REST APIs
      Real-time apps
      Custom frameworks
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Things people build with this

USE CASE 1

Build a high-performance Python REST API that handles many concurrent requests without blocking.

USE CASE 2

Add WebSocket support to a Python web server for real-time features like chat or live data feeds.

USE CASE 3

Create reusable middleware components that work across any ASGI-compatible Python framework.

USE CASE 4

Use Starlette as a foundation to build a custom Python web framework or toolkit.

Tech stack

PythonASGIUvicornJinja2

Getting it running

Difficulty · easy Time to first run · 30min

Requires running alongside a separate ASGI server like Uvicorn, not included as a required dependency.

Use freely for any purpose, including commercial projects, as long as you keep the original copyright notice.

In plain English

Starlette is a lightweight Python library for building web servers and APIs. It runs on a modern Python interface called ASGI, which allows the framework to handle many requests at the same time without blocking, making it well-suited for services that make network calls or do other work that involves a lot of waiting. You install it with pip, write your routes and handler functions in Python, then run it with a separate server program like Uvicorn. A minimal example involves defining a route (a URL path) and an async function that returns a response, and Starlette handles the plumbing between incoming HTTP requests and those functions. Starlette can be used in two ways. As a complete framework, it provides routing, request handling, WebSocket support, background tasks, middleware for compression and cross-origin requests, session and cookie support, template rendering with Jinja2, and a built-in test client. As a toolkit, individual components can be pulled out and used on their own without adopting the full framework structure. This modular design is intentional: it makes it possible to share middleware and application components across any ASGI-compatible project. The library has very few required dependencies. Optional features like templates, form parsing, sessions, and schema generation each require one additional package, but only those that are actually needed have to be installed. Starlette is fully type-annotated and claims 100% test coverage. It serves as the foundation that FastAPI builds on top of. The project is released under the BSD license.

Copy-paste prompts

Prompt 1
Build a minimal Starlette app with three routes, GET /items, POST /items, and GET /items/{id}, using async handlers.
Prompt 2
How do I add CORS middleware and gzip compression to a Starlette application?
Prompt 3
Show me how to handle WebSocket connections in Starlette for a simple real-time chat feature.
Prompt 4
Create a Starlette background task that sends a notification after an API endpoint returns a response.
Prompt 5
How do I write a test for a Starlette route using its built-in test client?
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